Piston



May 6, 1930 A c. R. BUTLER 1,757,169

PISTON Filed July 28, 1928 17.1311. A ,e Il' 2- ,5+

Ofi/P4 55 E @V7-55;

Patented May 6, 1930 PATENT OFFICE CHARLES R. BUTLER, OF INDIANAPOLIS, INDIANA PISTON Application led July 28,

It is the object of my invention to keep cool the head of the piston of an internal combustion engine.

To this end, it is my object to improve. the thermal conductivity between certaln regions of a piston structure, and more especlally between the piston head and the pistonA skirt, without thereby aifecting mechanically the shape of the piston. I

In a piston for internal combustion engines, the piston head receives a great guantity of heat from the hot gas which 1s d1- rectly in contact with it. This heat must be dissipated, in order to prevent the piston head from becoming too hot; as if the piston head becomes too hot serious consequences and even failure may ensue. Among such serious consequences are pre-ignition and detonation, and destruction of lubricant at the piston head and at the wrist pin; and the reduction of power and efficiency by the necessity of lowering the compression ratio to avoid such detonation. y

To avoid these difficulties, therefore, at least a large part of the heat received by the piston head must be carried. to the lowertemperature piston skirt, for dissipation therefrom both internally and externally.

On the other hand, in many piston structures, the-metal which is provided in the piston for mechanical strength and for normal control of thermal expansion is not sufficient in cross-section or properly located to serve 5 most advantageously as a heat conductor to transfer heat from the piston head to the piston skirt; with the result that the heat is stored up in the piston head, and such piston head becomes too hot. This is especially the case in heavy duty engines. This difficulty is augmented in certain modern pistons, in which the metal of the piston skirt is separated `more or less completely from the metal of the piston-ring belt by a transverse cir.

cumferential slit; and the piston skirt or various portions thereof are carried more orv less completely by the piston-pin bosses, which in turn are connected to the piston head. A

In carrying out my invention, I provide 1928. Serial No. 295,995.

relatively iexible metal connectors which extend between those parts of the piston between Which it is desired to increase the thermal conductivity. For instance, there may be such heat-conducting flexible connectors between the center of the piston head and the skirt below the piston-ring belt; and/or as spanners extending internally of the piston across the aforesaid circumferential slit between the piston-ring belt and the skirt; and/or between the piston skirt and the piston-pin bosses; and/or betweenV the piston skirt and webs that interconnect the piston-pin bosses to the piston head. In

general, these heat-carrying iiexible oonductors may be arranged between any two portions ofthe piston between which it is desired. to increase the heat conductivity without varying the mechanical reactions of one part of the piston on another; and especially between the piston'skirt and one or 'more piston parts which have a higher operating temperature than' has the piston skirt.

The accompanying drawing illustrates my invention: Fig. l-is a longitudinal section of one type of piston embodying my inventionthe section being taken substantially` on the axis of the piston pin and on the line 1-1 of Fig. 2; Fig. 2 is a partial elevation of the piston shown in Fig. land a partial section on the line 2-2- of Fig. 1, the view being taken looking at the end of the piston pin; Fig. 3 is a partial transverse section substantially on the line 3%-3 of Fig. 1;'l Fig. 4 is another partial transverse section through a piston embodying myl invention in a slightly different form, the section being taken on a transverse plane substantially corresponding with that on which Fig. 3 is taken; Fig, 5 is a longitudinal section taken substantially perpendicular to the piston-pin axis and showing my invention as applied to` a type of piston in which sections of the piston skirt are connected to the piston-pin bosses by metal of a different co-eicient of thermal expansion from that of the metal of the remainder of the piston; andFig. 6 is a partial longitudinal section and partial elevation ing the usual piston-ring grooves 12; pistonpin bosses 13, for receiving the usual piston pin; and a skirt 14 which may be either a continuous skirt joining directly to the rmgcarrying portion 11 of the piston head, as

shown in Fig. 6, or a skirt which is divided into sections by various slits or slots and/orv is mechanically separated4 from the 4ring-V bearing portion of the piston head instead of being continuous therewith, as -is shownin other iguresof the drawing. i

The various portions of the piston between which it is desired to increase thek heat conductivity areinter-connected by lexible conductors 15, of some suitable highly conductive material, such as copper; Which"lexible connectors have their ends embedded in the piston portions between which it is desired to increase the heat conductivity. These flexible conductors 15 are sufliciently flexibleto permit relative movement between the parts of -`the piston which they connect, lsuch ,as those due toc'hanges in temperature of the various A parts.

The various types of pistons shown willbe descnbed separately, so far as is necessary to an understanding of my present invention.

In the piston construction shown in Figs. 1, 2, and3, the. piston headlO'is connected to the piston-pin bosses'13 by struts or webs 20, shown as extending from the inner ends of the 'pistonepin bosses to the head at intermediate points on the diameter of the head. The

piston-pin bosses carry the pistonskirt 14,

which 1s shown as cutaway from the ,outer end of the bosses between the bosses and the piston head by crescent Islots21. The skirt 14 as a whole is separatedfrom-the rpiston- -ring belt 11 of the piston head by a circumf ferential s lit. 22, provided for reasons not here essentlal; so that such slit interrupts the `direct heat path from the piston-ring-.belt 11 to the skirt. The Skirt 14 is providedv with slits 23 which extend upward from the bottom of the skirt to about the level of the top ofthe piston-pin bosses 13, and'there terminate 1n a hole 24 provided to prevent cracking or splitting; the longitudinal slits 23 being spaced substantially 90 around the pisv ton from the axis of thepiston pin. Other slots 25 extend upward in the longitudinal .plane of the piston pin from the crescent slots 21 to the circumferential slit 22. The

piston as awhole, as thus far described, may be made of aluminum or some suitable aluminum alloy, or other relatively light metal and is shown as having embedded in it endless steel bands or rings 26 and 27 which are located in transverse planes above and below that of the piston pin. The steel bands 26 and 27 cross the slots 25 and 23 respectively.

According to the present invention, as applied to the type of pistonjust described and. shown in Figs. 1, 2, and 3, the heat-carrymgbelow the slot 22. The connectors `15 thus but the nature of Vthese is not essential here.

These relative movements may stilltake place substantiallyundisturbed by the flexible heat- .conductors 15, since the latter bend as neces sary to permit such relative movements as may occur. y

Instead of having the flexible conductors 15 extending between the piston skirt and the piston-ring'belt 11 of the head, or in addition to the heat conductors so located, I may provide heat conductors 15 which extend from the upper portion of the skirt 14 to the struts or webs 20.l This is illustrated separately in Fig. 4f; which shows thesame general type of piston as do Figs. 1, 2, and 3, but with the flexible conductors 15 dilerently arranged. It 'is illustrated in addition to the llexible heat conductors which directly interconnect the ring-belt portion and the skirt, in Figs. 1 and 3. The flexible conductors 15 in the piston of Fig.-4, and the additional flexible conductors between the skirt-and the struts in Figs 1 and 3', arebent in anysuitable shape which permits ready lexing, and have their inner ends embedded in the struts .or webs20 land their outer ends embedded in the skirt 14.

These conductors 15 serve to carry heat from the struts' or webs 20 to the skirt, and thus serve to facilitate the dissipation of heatfrom the piston head.

In the piston shown in Fig.' 5, thepiston -head 10 is connected to the piston-pin bosses 13 by webs 30 and.31, and 'the lpiston-pin bosses are connected -to skirt segments 14 by cross-struts 32. This is aknown construction, with the head and the skirt segments made of aluminum alloy and the cross-struts 32 made of steel. The cross-struts 32 have their ends .embedded in the skirt sections 14', and their ends of the skirt segments'14 as being joinedtogether, by .havingthem parts ofthe continuous or substantially continuous barrel Y portion 33 at the bot-tom of the piston, with a substantially longitudinal slot 34 extending upward from the lower edge 'of the piston skirt to about the transverse plane of the piston pin in one of the skirt segments 14 if that is desired; and with aluminuniconnecting members 35 extending upward from this lower barrel portion 33 to the piston-pin -bosses 13. As already stated, this steel-strut type of piston is already known, and I'have illustrated it merely to showthe application of my invention thereto.

According to my invention,v different parts of the4 piston shown in Fig. 5 may be interconnectedl byH heat-conducting flexible conductors 15. For instance, there may be such conductors between thepiSton-ring belt 11 of the piston head and the upper portions of the skirt sections 14', as shown at the righthand side of Fig. 5; and/or there may be flexible conductors 15 extending from the upper ends of such skirt segments 14 to the pistonin bosses 1:3, as indicated at the lefthan side of Fig.' v5. These conductors 15, in

` either or both of thelocations just mentioned or in other locations, serve to assist in carrying to the skirt segments heat which entered the piston by the piston lead, thus helpin to keep the piston head from becoming too ot.

Although my invention is of especial importance'when the piston skirt is not directly connected to the piston head, it isalso of value in the ordinary type of piston in which the piston skirt is so connected. This is illustrated in Fig. 6, where'the' piston shown is 4of a simple and conventional construction much used in cast-iron pistons, with the skirt 14 directly joining the piston-ring belt 11 of thee piston head, and with the piston-pin bosses 13 rprovided in such skirt. Here, to

. facilitate cool" ng of the piston head, and especially to avoid the frequent hot spot at the center of the piston head, I provide flexible conductors 15 which extend from the general middle portion of the piston head to the piston skirt above the piston-pin bosses, and which eectually keep the piston head suii- 'ciently cool.

My invention is applicable to many. other forms of pistons, which I need not describe here, since modiications necessary to apply my invention to these other types of pistons will be apparent from the foregoing.

I claim as my invention:

1. A piston.construction having various parts provided for mechanical strength, and which part's are capable of slight movement relative to and independent of one another,

and inaddition heat conductors applied to..

the piston structure to carry heat between portions of the piston over other paths than those available in the body ofthe piston, said 'heat conductors being flexible and of such shape that they bend readily upon relative movement between the piston parts which they. connect.y

2. A piston construction having various parts provided for lmechanical strength, and which parts are capable of slight' movement 'relative to and independent of-one another, and in addition heat conductors ap lied to the piston` structure to carry heat etween portions 'of the piston over other paths than those available in the body of the piston, said heat conductors being flexible and of such shape that they bend readily upon relative movement between the piston parts which they connect and in addition being of a-metal dierent from that of the body. of the piston and having their ends embedded inthe metal of the piston parts which they connect.

3. A piston, comprisingx a head having a piston-ring belt, a skirt which ismechanical- 1y separated -from said piston-ring belt, and

mechanical interconnections between the pis-` ton head and the skirt other than by way of a direct connection between the piston-ring belt and the skirt: and flexible conductors of high heat conductivity interconnecting .said skirt portion with said head.

4.,A piston, comprising a headhaving a piston-ring belt, a skirt which is mechanically separated from said piston-ring belt, and mechanical interconnections between the piston head and the skirt otherthan by way of skirt which is mechanically separated from said head at the periphery, and mechanical interconnections internally of the piston interconnecting Vthe piston head to the skirt;

and fieXible conductors of high heat conductivity connecting said 'skirt to piston parts which have a higher operating temperature than "the sln'rt.

7 A piston, comprising a head having a i piston-ring belt and depending struts separate from said piston-ring belt, piston pin bosses and a skirt carried by said struts, and iexible conductors of high heat conductivity interconnecting said skirt to said struts.

8.. A piston, comprising a head having a piston-ring belt and depending struts separate from said piston-ring'belt, piston pin bosses and a skirt carried by said struts, and

flexible conductors of high heat conductivity interconnecting said skirt both to said struts and to said head. In witness whereof, I have hereunto set my hand at Indianapolis, Inda-na,\this 25th day of July, A. D. one thousand nine hundred and twenty-eight.

CHARLES R. BUTLER. 

